Android编程实现canvas绘制饼状统计图功能示例【自动适应条目数量与大小】

本文实例讲述了android编程实现canvas绘制饼状统计图功能。分享给大家供大家参考，具体如下：

本例的目的是实现一个简单的饼状统计图，效果如下：

  

特点：

1.使用非常方便，可放在xml布局文件中，然后在代码中设置内容，即：

piechartview piechartview = (piechartview) findviewbyid(r.id.pie_chart);
piechartview.pieitembean[] items = new piechartview.pieitembean[]{
    new piechartview.pieitembean("娱乐", 200),
    new piechartview.pieitembean("旅行", 100),
    new piechartview.pieitembean("学习", 120),
    new piechartview.pieitembean("人际关系", 160),
    new piechartview.pieitembean("交通", 100),
    new piechartview.pieitembean("餐饮", 480)
};
piechartview.setpieitems(items);

2.条目数量，大小及折线位置，长度均自适应。左侧条目往左侧划线，右侧条目往右侧划线，文字描述与百分比居中对齐，并且文字“下划线”与文字长度自适应。对于很小的条目，将自动将折线延长以尽可能避免文字遮盖

核心代码：piechartview.java:

public class piechartview extends view {
  private int screenw, screenh;
  /**
   * the paint to draw text, pie and line.
   */
  private paint textpaint, piepaint, linepaint;
  /**
   * the center and the radius of the pie.
   */
  private int piecenterx, piecentery, pieradius;
  /**
   * the oval to draw the oval in.
   */
  private rectf pieoval;
  private float smallmargin;
  private int[] mpiecolors = new int[]{color.red, color.green, color.blue, color.yellow, color.magenta, color.cyan};
  private pieitembean[] mpieitems;
  private float totalvalue;
  public piechartview(context context) {
    super(context);
    init(context);
  }
  public piechartview(context context, attributeset attrs) {
    super(context, attrs);
    init(context);
  }
  public piechartview(context context, attributeset attrs, int defstyleattr) {
    super(context, attrs, defstyleattr);
    init(context);
  }
  private void init(context context) {
    //init screen
    screenw = screenutils.getscreenw(context);
    screenh = screenutils.getscreenh(context);
    piecenterx = screenw / 2;
    piecentery = screenh / 3;
    pieradius = screenw / 4;
    smallmargin = screenutils.dp2px(context, 5);
    pieoval = new rectf();
    pieoval.left = piecenterx - pieradius;
    pieoval.top = piecentery - pieradius;
    pieoval.right = piecenterx + pieradius;
    pieoval.bottom = piecentery + pieradius;
    //the paint to draw text.
    textpaint = new paint();
    textpaint.setantialias(true);
    textpaint.settextsize(screenutils.dp2px(context, 16));
    //the paint to draw circle.
    piepaint = new paint();
    piepaint.setantialias(true);
    piepaint.setstyle(paint.style.fill);
    //the paint to draw line to show the concrete text
    linepaint = new paint();
    linepaint.setantialias(true);
    linepaint.setstrokewidth(screenutils.dp2px(context, 1));
  }
  //the degree position of the last item arc's center.
  private float lastdegree = 0;
  //the count of the continues 'small' item.
  private int addtimes = 0;
  @override
  protected void ondraw(canvas canvas) {
    super.ondraw(canvas);
    if (mpieitems != null && mpieitems.length > 0) {
      float start = 0.0f;
      for (int i = 0; i < mpieitems.length; i++) {
        //draw pie
        piepaint.setcolor(mpiecolors[i % mpiecolors.length]);
        float sweep = mpieitems[i].getitemvalue() / totalvalue * 360;
        canvas.drawarc(pieoval, start, sweep, true, piepaint);
        //draw line away from the pie
        float radians = (float) ((start + sweep / 2) / 180 * math.pi);
        float linestartx = piecenterx + pieradius * 0.7f * (float) (math.cos(radians));
        float linestarty = piecentery + pieradius * 0.7f * (float) (math.sin(radians));
        float linestopx, linestopy;
        float rate;
        if (getoffset(start + sweep / 2) > 60) {
          rate = 1.3f;
        } else if (getoffset(start + sweep / 2) > 30) {
          rate = 1.2f;
        } else {
          rate = 1.1f;
        }
        //if the item is very small, make the text further away from the pie to avoid being hided by other text.
        if (start + sweep / 2 - lastdegree < 30) {
          addtimes++;
          rate += 0.2f * addtimes;
        } else {
          addtimes = 0;
        }
        linestopx = piecenterx + pieradius * rate * (float) (math.cos(radians));
        linestopy = piecentery + pieradius * rate * (float) (math.sin(radians));
        canvas.drawline(linestartx, linestarty, linestopx, linestopy, linepaint);
        //write text
        string itemtypetext = mpieitems[i].getitemtype();
        string itempercenttext = utility.formatfloat(mpieitems[i].getitemvalue() / totalvalue * 100) + "%";
        float itemtypetextlen = textpaint.measuretext(itemtypetext);
        float itempercenttextlen = textpaint.measuretext(itempercenttext);
        float linetextwidth = math.max(itemtypetextlen, itempercenttextlen);
        float textstartx = linestopx;
        float textstarty = linestopy - smallmargin;
        float percentstartx = linestopx;
        float percentstarty = linestopy + textpaint.gettextsize();
        if (linestartx > piecenterx) {
          textstartx += (smallmargin + math.abs(itemtypetextlen - linetextwidth) / 2);
          percentstartx += (smallmargin + math.abs(itempercenttextlen - linetextwidth) / 2);
        } else {
          textstartx -= (smallmargin + linetextwidth - math.abs(itemtypetextlen - linetextwidth) / 2);
          percentstartx -= (smallmargin + linetextwidth - math.abs(itempercenttextlen - linetextwidth) / 2);
        }
        canvas.drawtext(itemtypetext, textstartx, textstarty, textpaint);
        //draw percent text
        canvas.drawtext(itempercenttext, percentstartx, percentstarty, textpaint);
        //draw text underline
        float textlinestopx = linestopx;
        if (linestartx > piecenterx) {
          textlinestopx += (linetextwidth + smallmargin * 2);
        } else {
          textlinestopx -= (linetextwidth + smallmargin * 2);
        }
        canvas.drawline(linestopx, linestopy, textlinestopx, linestopy, linepaint);
        lastdegree = start + sweep / 2;
        start += sweep;
      }
    }
  }
  public pieitembean[] getpieitems() {
    return mpieitems;
  }
  public void setpieitems(pieitembean[] pieitems) {
    this.mpieitems = pieitems;
    totalvalue = 0;
    for (pieitembean item : mpieitems) {
      totalvalue += item.getitemvalue();
    }
    invalidate();
  }
  private float getoffset(float radius) {
    int a = (int) (radius % 360 / 90);
    switch (a) {
      case 0:
        return radius;
      case 1:
        return 180 - radius;
      case 2:
        return radius - 180;
      case 3:
        return 360 - radius;
    }
    return radius;
  }
  static class pieitembean {
    private string itemtype;
    private float itemvalue;
    pieitembean(string itemtype, float itemvalue) {
      this.itemtype = itemtype;
      this.itemvalue = itemvalue;
    }
    public string getitemtype() {
      return itemtype;
    }
    public void setitemtype(string itemtype) {
      this.itemtype = itemtype;
    }
    public float getitemvalue() {
      return itemvalue;
    }
    public void setitemvalue(float itemvalue) {
      this.itemvalue = itemvalue;
    }
  }
}

完整实例代码点击此处本站下载。

更多关于android相关内容感兴趣的读者可查看本站专题：《android图形与图像处理技巧总结》、《android开发入门与进阶教程》、《android调试技巧与常见问题解决方法汇总》、《android基本组件用法总结》、《android视图view技巧总结》、《android布局layout技巧总结》及《android控件用法总结》

希望本文所述对大家android程序设计有所帮助。